Many online services enable their users to communicate with the online service and/or or amongst each other using their mobile devices. For example, an online service may facilitate text messages, phone call communication, etc., between a driver and a rider, a customer and a business, or between any two users of an online service. While enabling users to communicate using their mobile devices is convenient, some users may be hesitant to provide their personal contact identifier (e.g., phone number) to people that they do not know. For example, a user of a ride sharing service may not wish to share their phone number with their assigned driver. Likewise, a restaurant patron may not wish to share their phone number with the restaurant at which they made a reservations. Accordingly, improvements are needed.